Perhaps a more important question is not about the risks of transmitting, but the dangers in receiving. Many in the SETI community have shown commitment to the belief that a technologically advanced civilization will be altruistic, despite the lack of evidence supporting that assumption. Therefore it is assumed there are no significant risks with listening quietly.
In an interview for Business Insider, astronomer and former director of the Center for SETI Research Jill Tarter, responded to Stephen Hawking's concerns about Active SETI, or sending messages to possible extraterrestrial civilizations rather than simply waiting and listening for signals from said intelligent aliens.
The extraterrestrials are just plain done with us. The Cold War has ended, and so has their fascination with our nuclear missile silos. So maybe they've just declared "mission accomplished," and gone away. That would be analogous to Charles Darwin's visit to the Galapagos Islands -- after he probed, bottled and cataloged some of the natives, he weighed anchor and withdrew. But here's another possibility.
Cosmologists propose that the universe was until recently a lifeless collection of particles. But they have ignored a critical component of the cosmos because they don't know what to do with it. This component, consciousness, is an utter mystery. How did inert, random bits of matter ever morph into Obama or Lady Gaga?